With the growth of the use of personal communication devices, e.g., cell phones and two way radios, high performance and high frequency packaging materials have increased in importance. Desired characteristics for electronic packaging include high electric and thermal performance, thinness, low weight, small size, high component density, and low cost.
When attaching an integrated circuit to a packaging material, e.g., a printed circuit board or a polymer material, it is known that the coefficient of thermal expansion (CTE) of the integrated circuit and the packaging material must be matched. When the CTE of the two materials are matched, the two materials will expand and contract simultaneously over temperature so as to avoid deformities, cracking, detachment, and loss of functionality, especially after a number of temperature cycles. The importance of this matched CTE becomes apparent in many applications having large temperature swings, e.g., automotive electronics.
Conventional packages are fabricated from materials such as plastic, Teflon or ceramics. The type of material that is used depends on a number of factors which include frequency of operation, environment and cost. Plastic packages are typically the lowest in cost but may not be suitable for high frequencies of operation or very high temperatures. Applications that require exposure to extreme temperatures will commonly use ceramics. The metallization that can be used will typically differ depending on the packaging material. As the frequency of operation increases, factors such as surface roughness and metal thickness become important. In addition to these factors, as the frequency of operation increases it becomes advantageous to utilize materials that have lower dielectric constants to allow for the implementation so that the final package, with interconnects, will avoid noise or signal loss associated with high speed circuits
One known solution is to place the integrated circuit on the substrate and within a hole formed in a liquid crystal polymer material; however, this adds complexity to the manufacturing process.
Another known solution involves the formation of a single layer of liquid crystal polymer between two non-liquid crystal polymer substrates; however, this results in layers that will not have as good a performance at a high frequency as liquid crystal polymer.
Accordingly, it is desirable to provide a liquid crystal polymer package that matches the CTE of an integrated circuit to that of the packaging material. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.